Keypads are used in electronic devices which require human input, particularly input of alphanumerical text. Examples of such electronics include, but not limited to, computers, laptops, portable handheld communication devices such as mobile phones and PDAs, facsimile, computer tablets, GPS navigation systems, electronic dictionaries, ATMs, and order and ticket kiosks. In most of these devices, input of alphanumerical text is performed by one or two fingers, or by an input vehicle such as a stylus, and ten-finger touch-typing option is not available.
While some keypads exist in conventional button-type keys, most keypads are implemented on touch screen displays for newer electronic devices. An advantage of touch screen keypad is that the input language, size and number of keys, and alphabet arrangement can be freely modified according to user preference. Further, touch screen keypads can employ various input mechanisms not available in keypads using button-type keys, such as drag and swipe mechanisms.
There are many types of keypad layouts depending on the input language and user preference. For English, two of the most widely known keypad layouts are the QWERTY keypad layout shown in FIG. 1, which is a miniature version of the alphabet arrangement of the computer QWERTY keyboard, and the 4 by 3 standard (ITU-T E.161) keypad layout (FIG. 2) employing either the conventional multitap input method (hereafter may be referred to as “the multitap method”) or T9 predictive text input method. The ITU-T E.161 standard keypad layout may hereafter be referred to as “the 12-key keypad”.
Vast majority of users are familiar with the QWERTY keypad alphabet arrangement and its method of operation. However, its large number of keys, which are often times displayed in a limited keypad area, results in small individual key sizes, which causes high error rate and discomfort to the user. Further, the QWERTY keypad layout is considered as an inappropriate choice for keypads operated by one or two fingers or by a stylus because of its poor aspect ratio (10:4) and ergonomically inefficient letter assignment. Ergonomic inefficiency of the QWERTY keypad layout has been well documented, although users familiar with the QWERTY keypad layout may not be consciously aware of it.
The 12-key keypad shown in FIG. 2 is an overloaded keypad layout. An overloaded keypad layout is hereby defined as a keypad layout having a number of keys available for letter input which is less than the total number of letters. Additionally, an overloaded key is a key to which multiple letters are assigned. In the 12-key keypad, only eight keys are available for actuation of twenty-six letters, and those keys are heavily overloaded with three or four letters. An overloaded key creates ambiguities as to which letter is intended for actuation by a single keystroke. The ambiguities are resolved, or disambiguated, by the multitap method. The user presses a key repeatedly to actuate the desired letter. While resolving the ambiguities, the multitap method also increases the number of keystrokes to enter a letter, which substantially increases the total number of keystrokes for a heavily overloaded keypad.
Another disadvantage of an overloaded keypad layout, such as the 12-key keypad of FIG. 2, is that entry of consecutive letters assigned to the same key cause further ambiguity. For example, when entering the word “cap” using the 12-key keypad of FIG. 2, the user must press the “abc” key four times, then the “pqrs” key once. However, this input sequence results in the following seven possible entries: “aaaap”, “aabp”, “acp”, “abap”, “baap”, “bbp”, and “cap”. Thus, the user input is still ambiguous since there are more than one possible outputs.
To disambiguate entries for consecutive letters overloaded in the same key, a short pause can be used. The user would wait a short amount of time which would allow the processor to “timeout” the ambiguity. From the example above of entering the word “cap”, the user would press “abc” key three successive times to actuate the letter “c”, pause to disambiguate, press the same key once more to actuate the letter “a”, then press the “pqrs” key once to actuate the letter “p”. Using this timeout method of disambiguation causes discomfort to the user since whenever there is an ambiguity, the user must pause between text input, momentarily stop the typing flow, and wait for a predetermined amount of time.
Discomfort due to timeouts can be partially solved in the multitap method by use of a delimiter key, also known as “timeout-kill key”. The delimiter key is a function key which is entered in lieu of a timeout. By pressing the delimiter key, the user signals the completion of an entry and “kills the timeout” so that any subsequent entry (or entries) after the delimiter key is associated with entry of a new letter. By pressing the delimiter key, the user can continue the input sequence without interrupting the typing flow. Alternatively, delimiter function, or timeout-kill, may be achieved by other actions, including drag-assisted motions.
Applying a delimiter key or an equivalent timeout-kill action for disambiguation still causes some discomfort to the user since it demands the user's attention to apply the delimiter key in the appropriate situations. Users who are not familiar with the multitap method may have difficulty understanding and/or operating the “timeout” and delimiter disambiguation methods.
A viable alternative input method to the multitap method is the selector (select-next-character) key input method, which resolves the ambiguity issues inherent in an overloaded keypad. The selector key input method, also known as the “conversion key” input method and may hereafter be referred to as “the selector method”, is a relatively new and not widely known input method. In the previously mentioned multitap method, the user presses the same key multiple times to actuate the desired character. However, in the selector method, the user presses the key associated with the desired character once, and presses a predefined selector key as many times as required to actuate the desired character. To enter the word “cap” using the 12-key keypad of FIG. 2 employing the selector method, the user would press the “abc” key once and the selector key twice to enter the letter “c”, then press the “abc” key once to enter the letter “a”, then press the “pqrs” key once to enter the letter “p”.
In both the selector and multitap methods, a desired letter is selected and tentatively actuated, that is displayed on the screen, by pressing a key associated with the desired letter and pressing for the requisite times the selector key or the said key associated with the desired letter, respectively. The selection of the desired letter is finalized when a key other than the selector key or said key associated with the desired letter is pressed. In the multitap method, the selection of a desired letter may also be finalized by a timeout or by pressing the delimiter key.
The multitap method and the selector method are further explained and compared here forth. The virtual keypad layout shown in FIG. 3 is substantially the same as the 12-key keypad of FIG. 2, but includes a delimiter key () and a selector key (). Table 1 shows the key entry sequences necessary to actuate various words using the virtual keypad of FIG. 3, contrasting the two input methods. In Table 1, the keys of the virtual keypad of FIG. 3 are denoted by their respective first alphabet letter, and the number of keystrokes are shown in parenthesis.
TABLE 1Desired outputEntry sequence (Delimiter)Entry sequence (Selector)1feedsddd   dd   dd   dpppp(15)d     d   d   dp       (12)2castaaa   appppt(10)a     ap       t (8)3monom   mmm   mm   mmm (11)mm     m   m     (8)4badeaa   ad   dd (8)a   add   (6)5cabinaaa   a   aagggmm (13)a     aa   g     m   (11)
Basic shortcomings of all known prior art approaches to designing an overloaded keypad layout are that they have ergonomically inefficient design, slow or cumbersome operating mechanisms, or that they are difficult to learn for the average user. Objects of the present invention are, therefore, to provide an overloaded keypad layout which is simple, efficient, ergonomic, unambiguous, intuitive to operate, and also familiar to the average user in its letter arrangement, and a method of designing the same.